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Monitoring system in one line :
DISK : disk space
MEM: memory ( mem , swap, Total)
CPU : all information about cpu activity
LOAD : load average
Output for human beings!
This command shows a high level overview of system memory and usage refreshed in seconds. Change -n 10 to you desired refresh interval.
Does not output the word "shared" so you can easily store this number in a variable.
Here we instead show a more real figure for how much free RAM you have when taking into consideration buffers that can be freed if needed.
Unix machines leave data in memory but marked it free to overwrite, so using the first line from the "free" command will mostly give you back a reading showing you are almost out of memory, but in fact you are not, as the system can free up memory as soon as it is needed.
I just noticed the free command is not on my OpenBSD box.
Check RAM size
simple way to show free swap